Mention “bacteria” and people begin looking for the germicide. The truth is, though, only a few strains cause disease — the rest are benign or even play a beneficial role.

This may shock you, but your body both inside and out is home to around 100 trillion single-celled organisms, exceeding the number of your native cells by 10 to 1. You won't notice them, though: bacteria are so small they only make up 1 to 3% of your total body mass. And each of us has a unique “microbiome” of micro-organisms: they influence a variety of processes like digestion and metabolism, and some even “teach” our immune systems to distinguish between helpful and harmful bacteria.

Of the 10,000 or more species of bacteria that inhabit the body, perhaps the most studied and understood are in the mouth. We even have a database that catalogs the gene sequences of oral bacteria. And what we've learned has enlarged our understanding of dental disease and how to prevent or treat it.

This new knowledge, for example, confirms that many of our modern lifestyle habits adversely affect oral health. For example, researchers have found higher concentrations of Streptococcus mutans, the bacteria most responsible for tooth decay, in current samples of biofilm than in those from preindustrial eras. The culprit seems to be the modern diet rich with carbohydrates like sugar that bacteria eat. Cigarette smoking can also make the mouth friendlier to disease-causing bacteria.

On the bright side, our growing knowledge of oral bacteria is helping us devise better prevention and treatment strategies. One example is the use of antibiotics to reduce the populations of disease-causing oral bacteria.

The broad, traditional approach kills not only malevolent bacteria, but beneficial strains as well. The approach may also be helping bad bacteria become resistant to common antibiotics. A newer approach targets specific bacteria with custom-designed antibiotics that won't kill other bacteria. There's also increased focus on ways to re-balance a person's normal microbiome if it's become skewed.

As we come to understand bacteria better — both good and bad species — these and other dental care efforts will benefit. With our increasing knowledge of these microorganisms that surround us the future looks bright for better oral health.